1. Field of the Invention
The present disclosure is generally related to aerial refueling booms and more particularly to systems and methods for estimating the elevation of an aerial refueling boom.
2. Related Art
Aerial refueling aircraft utilize refueling booms to transfer fuel from tanks within the refueling aircraft to an aircraft receiving the fuel while in-flight. Turning to FIG. 1, an example of an implementation of a known approach to refuel a receiving aircraft 100 with an aerial refueling aircraft 102 utilizing an aerial refueling boom 104 is shown. In this example, the aerial refueling boom 104 is pivotally mounted at one end 106 to the aerial refueling aircraft 102. The aerial refueling boom 104 typically includes a telescoping nozzle with a connector 108 at the opposite end of the aerial refueling boom 104. The nozzle connector 108 connects to a corresponding receptacle on the receiving aircraft 100. The aerial refueling boom 104 may be pivotally mounted to the aerial refueling aircraft 102 via gimbal type structure and the aerial refueling boom 104 may be lowered from and raised to the aerial refueling aircraft 102 via a combination of control surfaces 110 (that typically include elevator and rudder surfaces) and a hoist-cable 112. Once connected, fuel is transferred from the tanks within the aerial refueling aircraft 102 to the receiving aircraft 100 via the aerial refueling boom 104.
Generally, aerial refueling booms (such as aerial refueling boom 104) are designed to rotate upwards to the tail 114 of the aerial refueling aircraft 102 for stowage in a position that does not interfere with functioning of the aerial refueling aircraft 102 during operations and to minimize drag on the aerial refueling aircraft 102 when the aerial refueling boom 104 is not in use. As described earlier, during refueling operations, typical aerial refueling booms (such as aerial refueling boom 104) are designed to rotate downwards to a position for mating with the receiving aircraft 100 and for transferring fuel. To aid in the process of mating the aerial refueling boom 104 nozzle connector 108 to the receiving aircraft 100, the aerial refueling boom 104 may include the control surfaces 110 mounted to the aerial refueling boom 104. These control surfaces 110 may be manipulated by an operator aboard the aerial refueling aircraft 102 using a flight control stick (“FCS”) in order to “fly” (i.e., move and position) the aerial refueling boom 104 so as to guide, and align the nozzle connector 108 with the receptacle of the receiving aircraft 100, and then stow the aerial refueling boom 104. Additionally, the aerial refueling boom 104 may be extended and retracted utilizing an aerial refueling boom actuator utilizing a telescope control stick (“TCS”). Moreover, in addition to the control surfaces 110, the hoist-cable 112 is a secondary and/or auxiliary system for stowing the aerial refueling boom 104.
Unfortunately, known implementations of these types of systems are generally susceptible to a single point failure when moving the aerial refueling boom 104. Specifically, known aerial refueling boom systems utilize aerial refueling boom elevation and roll tilt axis inclination sensors that are quad-electric but dual-mechanical sensors. As such, in an example of a failure in the system, one sensor may have a mechanical shaft failure within the sensor and produce incorrect sensor outputs that will be the same for channel A and channel B. As a result, when comparing the channel A and channel B of the “bad” sensor to the channel A and channel B of the “good” sensor, the A/B channels of each sensor will agree but it will not be possible to know which sensor is correct.
As such, there is a need for a system and method that will allow accurate sensor measurements of the position of an aerial refueling boom when a sensor failure occurs in the system.